This invention relates to blow molding articles from a thermoplastic material and more particularly to an improved two-piece construction of a blow molded container with handle.
Bottles and other containers are conventionally blown from thermoplastic materials such as polyethylene, polypropylene, polyethylene terephthalate, and polyvinyl chloride. As an initial step in the manufacturing process, a preform is formed either by injection molding or by extruding a thermoplastic material into a hollow tube and blowing the extrusion into a preform. This preform is then transferred to a blow mold cavity where it is expanded to its final shape. However, problems have arisen when attempts have been made to blow mold containers having handles attached thereto.
When handles are integrally formed on the container during the blow molding procedure, a more complex molding cavity is required and problems such as poor material distribution in the final container, misalignment of the preform in the mold, welding failures, and difficulties in molding fast setting plastics such as polyvinylchloride have arisen. Uhlig, U.S. Pat. No. 3,983,199, describes in detail the problems associated with blow molding containers with integral handles. If the choice is made to separately attach a handle to a container after the blow molding operation is completed, different problems arise. Separately attached handles require an assembly operation which increases both the time and labor required to produce a finished article. Additionally, the handle must be securely attached to the container so that it will not separate from it at a later time.
As can be seen from the above discussion there is a need in the art for a method of producing blow molded containers having handles attached thereto which avoids the prior art problems and yet does not add substantially to the time and expense required to produce such a container.